Trace amounts of pharmaceuticals have been detected in water, from nanograms per liter to micrograms per liter, and have a negatively effect in the aquatic environment and an increased potential risk of drug poisoning for human and animals. In order to address the problem, drug degradation catalyzed by chloroperoxidase (CPO) has been investigated. CPO is a heme-containing glycoprotein secreted by the fungus, Caldariomyces fumago, it catalyzes two major types of oxidations, two one-electron oxidations as catalyzed by most peroxidases and two-electron oxidations which are rare for conventional peroxidases.
Five common drugs from a variety of classes which were persistent in the environment have been studied. The metabolites of each drug were identified and the pathways of degradation were proposed. All of them were found to be 100% degradation efficiency in the CPO-H2O2-Cl- system which the catalyzation only required low concentration of CPO (normally nanomolar level) as well as relatively low concentration of H2O2 as cofactor. This degradation method is economic and highly efficient, the results of my experiment extensively support the hypothesis that CPO has a great potential in the environmental application.
A new mutant of CPO has been constructed to investigate the role of histidine 105 in the active site of distal pocket. Histidine 105 was suggested to play an essential role in modulating the chlorination activity by forming hydrogen bond with glutamic acid 183, histidine has been replaced by arginine to generate CPO H105R mutant. The construction and transformation were a success but the protein was expressed as apoenzyme, suggesting the mutagenesis to a larger arginine residue at position105 disturbed the heme incorporation.
